Conventional machines for solid phase polymerization are roughly classified into two types. One is a batch type machine, such as a rotary cylinder type or a tumbler type, and the other is a continuous type machine, such as that having a helical vane for agitating and feeding or having a plurality of rotary discs. However, generally speaking when such machines are used for solid phase polymerization of, for example, polyester particles, which are usually formed in a cylinder or a polygonal prism, which have a width and a length of between 2 and 6 mm, and which are called chips, generation of stuck chips wherein chips are stuck to each other, cannot be avoided. Therefore, the produced chips withdrawn from a conventional machine for solid phase polymerization are selected by passing them through a sieve. However, the conventional machine is disadvantageous in that the quantity of stuck chips is very large, and accordingly, productivity thereof is low. Especially, in a continuous type machine, such a problem often occurs because time for pre-crystallization is short, and if a selection system utilizing a sieve is applied, the continuity of the process is disturbed.
Tumblers, wherein a vacuum seal can be made most easily among the above-explained systems, have also been widely utilized as machines for solid phase polymerization. However, since such tumblers along to a batch type, their production capacity per unit time is small since a long reaction time is required. In addition, their operation is troublesome and an uneveness occurs in the quality of the obtained chips between the batches.